Instructions
Play through the game until you reach Lavender Town. The game takes you here naturally.
Enter the Pokemon Tower, which has a descriptive sign near the entrance.
Fight all of the trainers inside of the tower. Defeating all of their Pokemon will allow you to turn the power back on. Exit the tower.
Press "A" to talk to the old man outside of the tower. He will thank you and give you the Expansion Card.
Return to Snorlax on Route 11, marked on your in-game map. Walk up to it and press "A" to initiate battle. Defeat or capture Snorlax to move him out of your way.